Drain Embedded in Concrete Slab in Condo Complex

My first post. Thanks in advance for all your time. I am in the process of changing a bathtub into a shower. Ripped out the pre-fabbed fiber-glass tub and surround, and found the drain pipe is embedded in concrete. First of all, I discovered that showers should be outfitted with a 2" drain, so this drain pipe has to be switched out (it currently is 1.5" for the previous tub). Second, I live in a newer condo complex in California on the third floor. I have a neighbor below me so I'm apprehensive about jackhammering up concrete, especially when I don't know what's underneath. I uploaded some pictures I took of the uneven concrete we uncovered.

My questions are:

Despite my apprehension, would it be advisable to demolish the concrete to change out the pipe?

How would I most safely and slowly do this without risking any damage to my downstairs neighbor's property?

Do you think getting to the pipe will be easy after getting through the concrete?

What typically lay under concrete slab like this in a newly built condo complex?

What other things should I be keeping in mind from here on out (I'm a bit of a newbie, so I'm anticipating a lot of flaming replies. )

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I'd guess that the slab is poured around the top part of the drain riser, but the p trap and trap arm are below it, in your downstairs neighbors ceiling. If someone also lives above you, pull one of those bathroom can light trims to take a peek above your own ceiling. You should see drain pipe for upstairs neighbor running up through a sleeve in the deck.

You won't be able to do the drain work without impacting the people downstairs.

Also, how many floors does this building have? You don't want to do ANY jackhammering, or slab removal until you know what kind of building this is. If the slabs are post tension, and you pop a cable, you're going to be in deep shit. They are structural elements.

1.If it is "post tension", which is very possible if all the floors are concrete, you may not even be allowed to cut or drill the concrete, at least not without some engineering approvals.
2. YOU cannot do any of those things, because the association SHOULD require than any work of this type be done by a licensed AND INSURED contractor., which you are neither.
3. You are assuming that there is a 2" drain line available for the shower, which may not be the case.

Thanks for the replies, guys. You're right, I do not know if the floors are post-tension or not. The entire bldg is earthquake retrofit (see the metal studs in the pictures) so I'm guessing that post-tension would be the best way to build the floors.

I'm wondering if the post-tension slab would have been laid, though to embed the pipe in it? Post-tension concrete, the way its built, has to be laid in a factory in order to tension the metal cables inside of them at 70% dryness.

Pre-tensioning requires strong, stable anchoring points between which the tendons are to be stretched. Thus, most pre-tensioned concrete elements are prefabricated and transported to the construction site, which may limit their size.

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There's no way they would have laid post-tension concrete around a pipe like this. I'm thinking that this might be an overlayment of concrete on top of a possible slab of post-tension concrete. I'm still making half-educated guesses though and won't make any cuts until I'm 100% sure. I'd love to get feedback from anyone who has had experience in pulling up a pipe in a condo complex like this before.

Vegas-sparky: I like your suggestions. I live on the top floor of a three story complex. They are actually condo/townhomes. So I wouldn't be able to see a like-scenario on an above-neighbor. Brilliant idea though.

Does anyone know how to get the building plans to a complex such as this? The Association doesn't know much about it. I should know, I'm on the board. They've admitted that they lost contact with the builder years ago and are very hard to locate. Are building plans part of public record somehow? If a contractor was in this same position, how would he go about finding out what lay in that concrete floor?

Are you sure that is concrete and not gypsum? Can't tell from the picture, but gypsum is sometimes used to level and help provide some additional sound isolation. If gypsum, it should be easy to scratch with say something like a screwdriver. Course, that could be on top of concrete as well.

Depending on the city, some of them will have blueprints from when the building permit was applied for.

There is always an initial Public Offering Statement when the units are sold from the builder / developer. That P.O.S. would have included plans. Like jadnashua said, the city may have them, but if city is anything like Seattle, good luck finding them.

Most condo associations have it worded so that almost anything beyond the paint, the association has the right to step in, and stop you from what you're doing, and require proper licensed labor etc. Especially when you start getting into wall and floor spaces that affect neighboring units, or electrical.

I hate people making a big deal about nothing, but...this really is serious. If you were to affect a common plumbing or electrical element, or heaven forbid something structural, you would be liable, and no insurance would cover that - you could easily go bankrupt if an issue were to arise. So you really should hire a professional. You already saved a lot money doing the tear out.

That link for post tension doesn't explain everything. I've helped build every tower in Vegas for the past 20 years. We have seismic requirements also. Here, when floor decks are formed, the sheathed, greased PT cables are laid on top of the rebar, and extend out the edges of the floor. After the decks are poured and cure for x amount of time, tension is applied with hydraulic pullers, and special fittings applied to hold the cable and keep the slab under compression. These cables are laid according to specific engineering details, and are seldom in a straight path. Basically they can be almost anywhere. Any penetrations through the the deck afterward are preceeded by an investigative x-ray of the deck before they're made. I've seen them hit by electricians looking for buried conduit. Because of the tension, just nicking the cable can cause it to fail. The entire floor shakes when one lets loose. Its unnerving, and engineers must evaluate the consequences. Repair is expensive.

I get the impression you think the horizontal drain line from the shower is embedded in the concrete. That's not typical for my area. All the drain lines should be underneath the deck, with only the risers extending up through it. You would have to have the ceiling below your bathroom opened up to investigate, and possibly change what you have. You can do all the other work yourself, but this drain is a place you don't want to go by yourself.

Find a friendly neighbor on the second floor, pop one of their bathroom lights out, and see for yourself. The camera on your Cel phone can be stuck up there to take lots of pictures. You have to know exactly what you're dealing with. Your local building department should have full sets of plans.

No ones flaming you. Just trying to help you avoid a very serious mistake. With the demo done, you're already committed to a renovation.

Thank you guys for the advice. Yes, it would make the most sense if I could get a downstairs neighbor to let me take apart one of their recessed lights. I am pretty sure there's a layer of insulation that we'd have to cut through too to get any kind of visual of it. Sounds like a sticky situation even if professional contractor were involved. But even then, he'd have to worry about if the floor was post-tension or not. Do plumbers typically have xray machines where they can analyze a floor on any given day? I can't imagine having to worry about post-tension floors each time a drain problem was unsurfaced. Also, this condo isn't a high rise in a metropolitan area. It's a humble town in the Bay Area, probably not worth the effort of putting all that work into a post-tension floor. However, I don't have the same experience you do, so I'm not sure how common this is.

As long as you stopped thinking about jacking up the floor, you're good. That activity had to cease.

Post tension or not, the drain lines go vertically through the deck, either through sleeves installed before it was poured, or core holes made afterward. As soon as they are below your floor (and in the DS neighbors ceiling), they hit their p trap, then turn horizontally towards a wall where they typically attach to the common DWV risers. The point is that the drains are not buried in the concrete. They only pass through the cross section of the deck.

The drain lines can be changed, you don't have to destroy your entire floor or even x ray. You would have to destroy the downstairs neighbors ceiling(and maybe some walls) to change the pipe. If you can gain access, and see the bottom of one of those decks, it'll all make sense.

Here's a really crude diagram just to explain where things could be in relative elevation(tub/deck/drains/ceiling). If its a wood framed deck the drain lines may pass horizontally through the floor joists, and technically might not be able to be enlarged. The horizontal drain line could go any direction, but typically towards other fixtures so they all dump into the common riser. Does that make sense to you, and do you see why you shouldn't even have to jackhammer the floor to find a drain line? You REALLY need a pro plumber to look and see if this 2" drain is feasable.

Here's a really crude diagram just to explain where things could be in relative elevation(tub/deck/drains/ceiling). If its a wood framed deck the drain lines may pass horizontally through the floor joists, and technically might not be able to be enlarged. The horizontal drain line could go any direction, but typically towards other fixtures so they all dump into the common riser. Does that make sense to you, and do you see why you shouldn't even have to jackhammer the floor to find a drain line? You REALLY need a pro plumber to look and see if this 2" drain is feasable.

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That's an amazing sketch! Thanks for this! That pipe riser that goes through the floor is pretty much what I had in mind. I just didn't know if there'd be another platform below the pipe before my neighbor's ceiling. From what your diagram shows, and from your past experience in Vegas, it sounds like there isn't an extra platform until the ds neighbor's ceiling and the pipe. I'm having a plumber come and check it out this week. Would plumbers be the ones to ask about this? Thanks again for the awesome drawing.

Oh and jadnashua, I'm not sure if it's gypsum or not. Even if it is, I'd have to jackhammer it up? I tried scratching it with the edge of a crowbar and it definitely leaves a mark, but the mark didn't stay there. It seems to have disappeared overnight. Are there any other ways that I could tell it's gypsum?

What you have there is a standard waste and overflow. The p-trap will be below the slab.
More than likely, there is a 4x12" cutout in the concrete floor for your tub drain. You may be able to tap that out if it's just mortar filling in the hole.
I doubt that you have a 1.5" trap arm there. You may have a 2"
If you have a 1.5", that would still drain the shower.

It was an awesome drawing.
It does not show the proper venting. There should be a vent stack, and a waste stack. The tub arm vents "before" entering the waste stack. You're allowed five feet on a 2" trap arm before the vent.

Thanks for the picture Terry! This is exactly what I wanted to see. I'm gaining hope that my floor isn't post-tension as originally thought. And I just found a small hint that there might be a wood surface only 1" below the concrete, similar to what your photo showed.

I moved some of the insulation out of the way and found a wood floor underneath an incomplete concrete pour. So this might be what I was hoping for. Do you guys think that the concrete pour is above a wood subfloor with this picture?

Some apartments are wood framed with "light weight" concrete poured over the plywood floors. This is a 1.5" pour. We block around the toilet (closet flange) and normally a 2x4 flat for the tub apron to set on.

Some apartments are wood framed with "light weight" concrete poured over the plywood floors. This is a 1.5" pour. We block around the toilet (closet flange) and normally a 2x4 flat for the tub apron to set on.

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Terry, how hard is this to demolish? Does it require a jackhammer since it's only a 1.5" pour?

Some apartments are wood framed with "light weight" concrete poured over the plywood floors. This is a 1.5" pour. We block around the toilet (closet flange) and normally a 2x4 flat for the tub apron to set on.

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Oh and would you recommend this to be done when the new shower or tub gets put in too? If so, is it just a simple or of concrete for the tub or shower to situate on?